System for demarcating an area

ABSTRACT

A system for demarcating an area comprises a movable demarcating element, and a control system for determining the magnitude and/or the moment of a next move of the movable demarcating element. The system furthermore comprises one or more observation devices for observing an entity near the movable demarcating element, such as a position of a dairy animal or an amount of grass in the area. The observation devices are operatively connected to the control system for transmitting a signal from the observation means to the control system. The control system is designed to receive and process the signal from the observation means to determine the magnitude and/or the moment of the next move of the movable demarcating element.

This application is a continuation of international application no.PCT/NL2007/000249, filed on Oct. 2, 2007, and claims priority fromNetherlands application no. 1032663 filed on Oct. 11, 2006. The contentsof both applications are hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system for demarcating an area, in particularfor limiting the freedom of movement of free-roaming animals, accordingto the preamble of claim 1.

2. Description of the Related Art

European patent 1,139,725 discloses a system for demarcating an area onwhich cows graze. The system comprises two or more self-propelledvehicles between which an electrified wire runs. Each of the vehicles isprovided with a GPS receiver. By means of the GPS receivers, thevehicles are able to determine the distance between them. The vehiclesare remotely controlled by a computer in such a manner that they movethe electrified wire together. In this way, it is possible in each caseto make a new part of the area available for the cows. The computer canin this case be programmed in such a manner that the vehicles moveaccording to a predetermined pattern at predetermined points in time. Inthis case, the computer has to be provided with information regardingthe shape and dimensions of the area, including the presence of ditches,fences and any other obstacles.

It is a drawback of the abovementioned system that it does not alwaysmake an optimum amount of grass available in practice. Some of the time,too much grass may be made available, as a result of which cows onlygraze in the more attractive parts of the area and defecate on grasswhich has not yet been eaten. By contrast, at other times, too littlegrass may be made available. As a result thereof, in practice, a user isforced to check whether the amount of grass which is made available iscorrect and, if not, to make adjustments himself, if desired.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to eliminate the abovementioneddrawbacks at least partially or at least to offer an alternative. Inparticular, it is an object of the invention to provide a system fordemarcating an area, in which a user does not have to check the size ofthe area which has been made available or at least check to a lesserextent.

This object is achieved according to the invention by a system fordemarcating an area, in particular for limiting the freedom of movementof free-roaming animals, comprising a movable demarcating element, and acontrol system, designed to determine the magnitude and/or the moment ofa next move of the movable demarcating element. The system furthermorecomprises one or more observation devices for observing an entity nearthe movable demarcating element, such as a position of a dairy animal oran amount of grass in the area. The one or more observation devices areoperatively connected to the control system for transmitting a signalfrom the observation devices to the control system. The control systemis designed to receive and process the signal from the observationdevices in order to determine the magnitude and/or the moment of thenext move of the movable demarcating element.

On account of the one or more observation devices, the system can adaptthe magnitude and/or the moment of the next move to the circumstancesprevailing at the time, such as a position of a dairy animal or anamount of grass in the area. Thus, the size of the area to be madeavailable will match the actual need of the animals present in the areamore closely, so that a user does not have to check whether the size ofthe area is sufficient, or at least to a lesser extent.

In particular, the one or more observation devices comprise at least oneof the following: a light sensor, a climate sensor, a milk sensor, asound sensor, a feed-dispensing sensor and a position sensor connectedto an animal. A light sensor and a climate sensor can provideinformation on the expected growing speed of grass and/or on theexpected need for grass of the animals which are present in the area. Amilk sensor can provide information about the amount and/or the qualityof the milk which is produced by the dairy animals which are present inthe area, which is a measure of the availability and the quality of thegrass in the area. A sound sensor can provide information about the feedhabits of the animals which are present in the area. A feed dispensingsensor can provide information on the amount of feed, not includinggrass, which is dispensed to individual animals and/or to all of theanimals present in the area. A position sensor which is connected to ananimal provides information about whether the animal is located at anarbitrary position in the area, which indicates that there is stillsufficient grass, or whether the animal is near the demarcating element,because it is longing for the grass which is located outside theavailable area.

In one embodiment, the one or more observation devices comprise a camerafor forming an image of the surroundings of the movable demarcatingelement. Various items of up-to-date information can be derived fromsuch an image, such as, inter alia, the positions of animals and theup-to-date orientation of the demarcating element.

In one embodiment, the camera comprises a source of radiation foremitting electromagnetic radiation, in particular light, a matrix havingseveral rows and several columns of receivers for receivingelectromagnetic radiation reflected by an object, such as an animal, alens for displaying the reflected electromagnetic radiation on thereceivers, and a sensor control unit, wherein the sensor control unit isoperatively connected to the source of radiation in order to modulatethe electromagnetic radiation, for determining a phase difference foreach of the receivers between the emitted and the reflectedelectromagnetic radiation.

Such a camera produces a reliable three-dimensional image in the form ofdistance or depth information for several points on a visible object tothe camera. Such a camera is relatively inexpensive and generates thethree-dimensional image in a short amount of time.

The following is an explanation of the operation of a possible camera.The source of radiation emits electromagnetic radiation. Preferablylight is used for this purpose, more preferably infrared radiation, morepreferably near-infrared (NIR) radiation. The fact is that, for thispurpose, suitable LEDs can be used which are very easy to drive by meansof an electrically controlled supply current, and which are, inaddition, very compact and efficient and have a long service life.However, it is also possible to use other sources of radiation. Theadvantage of (near-)infrared radiation is that the radiation does notirritate the dairy animals.

The radiation is modulated, for example amplitude-modulated, inaccordance with a modulation frequency which is, of course, differentfrom and is much lower than the frequency of the electromagneticradiation itself. The, for example, infrared light is in this case acarrier for the modulation signal.

By means of the emitted radiation, the distance is determined bymeasuring a phase shift of the modulation signal, by comparing the phaseof the reflected radiation with the phase of the reference radiation.For the latter, the emitted radiation is preferably (almost) directlypassed on to the receiver. The distance can easily be determined fromthe measured phase difference by applying: distance=½×wavelength×(phasedifference/2π), wherein the wavelength is that of the modulation signal.Note that the above relation does not make any allowance yet for uniquedetermination of the distance which results from the fact that a phasedifference, due to the periodicity, may be associated with a distance A,but also with A+n×(wavelength/2). For this reason, it may be sensible tochoose the wavelength of the amplitude modulation in such a manner thatthe distances which occur in practice are indeed uniquely determined.

Preferably, a wavelength of the modulation, for example amplitudemodulation, of the emitted radiation is between 1 mm and 5 m. Hereby,distances can be uniquely determined up to a maximum distance of between0.5 mm to 2.5 m, which is associated with a modulation frequency ofbetween 300 MHz to 60 kHz, which can be readily achieved in electriccircuits for driving LEDs. It should be noted that it is also possibleto choose smaller or larger wavelengths, if desired.

In one embodiment, the system furthermore comprises a first vehicle andthe control system is designed to transmit a control signal to the firstvehicle for moving the demarcating element. By incorporating a vehicleof this type in the system, the latter can make an area availablecompletely automatically, depending on the observed circumstances in andaround the area.

The invention also relates to a method for demarcating an area. Themethod includes providing a movable demarcating element, a controlsystem, and one or more observation devices operatively connected to thecontrol system. The method includes further steps of observing via theone or more observation devices, an entity near the movable demarcatingelement, transmitting a signal from the one or more observation devicesto the control system, receiving in the control system the signal fromthe one or more observation devices, and processing the signal todetermine the magnitude and/or the moment of the next move of themovable demarcating element.

The step of observing via the one or more observation devices maycomprise observing using at least one of the following: a light sensor,a climate sensor, a milk sensor, a sound sensor, a feed-dispensingsensor, and a position sensor connected to an animal. The step ofobserving may also comprise measuring an amount of milk produced by atleast one dairy animal, or measuring the composition of the milkproduced by at least one dairy animal, or forming an image of thesurroundings of the movable demarcating element.

The camera may comprise a source of radiation for emittingelectromagnetic radiation, a matrix having a plurality of rows andcolumns of receivers, a lens, and a sensor control unit operativelyconnected to the source of radiation, and the method may furthercomprise emitting electromagnetic radiation from the source ofradiation, receiving electromagnetic radiation reflected by an objectusing the receivers, displaying the reflected electromagnetic radiationusing the lens, modulating the electromagnetic radiation using thesensor control unit, and determining a phase difference between theemitted and the reflected electromagnetic radiation for each of thereceivers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail below with referenceto the attached figures, which show a non-limiting exemplary embodiment,in which:

FIG. 1 shows a first unmanned vehicle according to the invention, nextto a fence;

FIG. 2 shows a second unmanned vehicle according to the invention;

FIG. 3 shows the first unmanned vehicle from FIG. 1 next to a ditch; and

FIG. 4 shows a control circuit for the first and/or second unmannedvehicle.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The following is a description of certain embodiments of the invention,given by way of example only and with reference to the drawings. FIGS. 1and 3 show a first unmanned vehicle 1 which is provided with ademarcating element 2. The first unmanned vehicle 1 is inside an area,such as a pasture, which is already partly demarcated by means of afence 4 (FIG. 1). In the present exemplary embodiment, both thedemarcating element 2 and the fence 4 are designed in the form of a wirewhich can be electrified.

The first vehicle 1 in this exemplary embodiment comprises a frame 5having four cage wheels 6. The cage wheels 6 have a running surfacewhich is formed by convex strips 7 which are spaced apart from oneanother. The left-hand and right-hand pairs of cage wheels 6 eachcomprise a drive belt 8 which drives one pair of cage wheels 6 at a timeby means of an electric stepping motor 9, one of which is arranged onthe frame 5 for each separate pair of cage wheels 6 (see FIG. 2).Driving the electric stepping motors 9 simultaneously or independentlyof one another makes it possible to control the unmanned first vehicle1.

In order to be able to tension the demarcating element 2 between a firstvehicle 1 and a second unmanned vehicle 10, as illustrated in FIG. 2,the first vehicle 1 in this exemplary embodiment is provided with atensioning device 11 for tensioning the demarcating element 2 betweenboth vehicles. The tensioning device 11 comprises a winding device 13which can be driven by an electric motor 12 for winding up and unwindingthe demarcating element 2. As the first vehicle 1 and the second vehicle10 are essentially identical except for the tensioning device 11,identical parts are denoted by the same reference numerals.

The winding device 13 is attached to the frame 5 in a first suspensionpoint by means of a load cell (not shown) and to a further part of theframe 5 in a second suspension point by means of a leaf spring (notshown). A guide piece 17 which can be rotated about a vertical shaft 16is also arranged on the frame 5, via which guide piece 17 thedemarcating element 2 is guided to the winding device 13.

As is illustrated in FIG. 2, the guide piece 17 is provided with a loadcell 18 for determining the tensioning force of the demarcating element2 on the second vehicle 10. The end of the guide piece 17 is furthermoreprovided with a break-away protection 19 to which the guide element 2can be attached. In the present invention, the break-away protection 19is designed as a spring break-away protection which comprises a helicalbending spring 20 having a round cross section. If the tensioning forcewith which the demarcating element 2 is held between the two vehicles 1,10 exceeds a certain maximum value, the eyelet fastening is catapultedfrom the spring break-away protection. It will be clear that the eyeletfastening can be inserted back into the spring break-away protection ina simple manner by an operator without it being damaged.

The guide piece 17 furthermore comprises an angle gauge 21 by means ofwhich the angular rotation of the guide piece 17 on the vertical shaft16 can be determined. If the angular rotation exceeds a predeterminedmaximum angle, the vehicle is not driven further in order to prevent thetensioning force of the demarcating element becoming excessive. Thistensioning force and the fact that driving of the vehicle stops whenthis tensioning force is exceeded can be measured in the first vehicle 1by means of the load cell of the tensioning device 11.

On the frame 5 of, in this exemplary embodiment, both the first 1 andthe second vehicle 10, a camera is provided, in this case a combined2D/3D camera 100. The 2D/3D camera 100 comprises a plastic housing 101which is movably connected to the frame 5 via a ball joint (not shown).By means of the ball joint, the 2D/3D camera 100 can rotate about avertical axis and tilt about a horizontal axis using actuators (notshown), for example actuating motors.

Alternatively, the 2D/3D camera 100 may be fixedly connected to theframe 5, connected by means of a joint which essentially allows rotationabout a vertical axis, or connected by a joint without actuators.

The housing 101 comprises a front side 104. In the front side 104, alens 106 and several sources of radiation, in this exemplary embodimentlight sources 108 in the form of infrared light-emitting diodes (IRLEDs), are accommodated. In a variant, the lens 106 is provided on theinside of the front side 104, the front side 104 being made from amaterial which allows infrared light through. In this manner, the lens106 is protected from external influences and the flat plastic frontside 104 can be cleaned more easily than the front side 104 having aprotruding lens 106.

The housing 101 further accommodates a position-sensitive sensor, suchas a CMOS image sensor 110. On a side facing the lens 106, the CMOSimage sensor 110 comprises a matrix with several rows and columns ofreceivers, in the form of light-sensitive photodiodes. In this exemplaryembodiment, this is a matrix of 64×64 photodiodes, but resolutions of176×144, 640×480, and other, smaller or greater, matrices are likewisepossible. The CMOS image sensor 110 comprises an integrated sensorcontrol unit which drives the IR LEDs 108 and which process the infraredlight which impinges on each of the photodiodes to form a digital signaland pass this onto a central processing unit or computer via a wireless(not shown) or wire connection (also see below).

The sensor control unit of the 2D/3D camera 100 determines the distanceof an object relative to the each of the photodiodes by means ofmeasuring a phase difference between the light which is emitted by theIR LEDs 108 from the 2D/3D camera 100 to an object and the light whichreturns, after having been reflected, to the 2D/3D camera 100, i.e. tothe CMOS image sensor 110 thereof.

In an advantageous embodiment, the IR LEDs 108 emit anamplitude-modulated wave light signal. The amplitude modulation itselfhas a repetition frequency. Following reflection, this light signal isdisplayed on the CMOS image sensor 110 by the lens 106. By determiningthe phase difference of the received modulated light signal compared tothe emitted modulated light signal, it is possible to calculate thedistance between sensor and object by means of the wavelength of themodulated signal. This is carried out simultaneously for each of thephotodiodes on the CMOS image sensor 110. Thus, a spatial orthree-dimensional image of the observed object is produced.

It should be noted that the distance has not yet been uniquelydetermined in this manner. After all, an object may be at a distancefrom the sensor which is a multiple of wavelengths of the light signalused. In practice, this can be solved, for example, by varying thefrequency of the amplitude modulation as well.

In a particular embodiment, short light pulses may be emitted by the IRLEDs 108, provided each light pulse comprises at least one whole,preferably two or more, waves of the modulated signal.

Depending on the selected frequency of the amplitude modulation, the2D/3D camera 100 can take several, for example fifty, images per second.Each image is in this case to be regarded as a reliable representationof the observed object, such as the fence 4 (FIG. 1), a ditch 114 (FIG.3), grass, or a cow.

In addition to a spatial image, the CMOS image sensor 110 in thisexemplary embodiment can also generate a 2-dimensional image, in whichdifferences in color and reflection of the observed object are convertedinto different shades of gray.

FIG. 4 diagrammatically shows a vehicle control unit or vehicle controlunit means, in this case in the form of a control system 120. Thecontrol system 120 comprises a central processing unit 122 for drivingone or more actuators 124, and a user station in the form of a personalcomputer (PC) 126. The actuators 124 comprise the motors 9 and 12 and,optionally, the actuating motors (not shown) for directing the 2D/3Dcamera 100 itself. The 2D/3D camera is operatively connected to thecentral processing unit 122, in this exemplary embodiment via a wireconnection.

In this exemplary embodiment, the central processing unit 122 isprovided in a position (not shown) on the frame 5 of the first vehicle1, while a separate central processing unit (not shown) is provided onthe second vehicle 10. The central processing unit 122 is designed toperform various tasks, which are to be described in more detail below.To this end, the central processing unit 122 in this exemplaryembodiment has a working memory and is programmed using control softwareand interprets the images of the 2D/3D camera 100 on the basis ofalgorithms, and/or fuzzy logic control. Based on this interpretation,the central processing unit 122 drives one or more actuators 124, aswill be described in more detail below.

The central processing units 122 of the first unmanned vehicle 1, thesecond unmanned vehicle 10 and of any more unmanned vehicles (notshown), are connected to the PC 126 via a fixed, or preferably wireless,connection. The control software of the central processing unit 122 canbe loaded and/or modified via the PC 126. In addition, a monitor of thePC 126 can display an optionally edited image from the 2D/3D camera 100.This screen can also display any warnings, if the central processingunit 122 determines, based on the image from the 2D/3D camera 100, thata failure or other undesirable event is occurring.

Finally, the PC 126 may be provided with, or may be connected to,further peripheral equipment, such as a storage medium (not shown), onwhich images from the camera and/or edited information can be stored.The PC 126 may be the same PC which is also used to perform other tasksof, for example, a diary farm, if desired incorporating the function ofdriving the unmanned vehicles 1 and 10. The PC 126 may also form part ofa network of computers which together, for example, carry out variousprocesses on the dairy farm, such as farm management and controlling andmonitoring milking robots.

The central processing unit 122 of the first unmanned vehicle 1, andoptionally that of the second unmanned vehicle 10 and any more unmannedvehicles (not shown), are connected, via a fixed or wireless connection,to one or more observation devices designed to observe an entity nearthe movable demarcating element. As an alternative or in additionthereto, such observation devices can also be connected to the PC 126.The observation devices in this exemplary embodiment are theabove-described 2D/3D camera 100, a climate sensor 130 and a milk sensor132.

The control system 120, and in this exemplary embodiment the centralprocessing unit 122 in particular, are designed to receive and process asignal from the observation devices 100, 130, 132. The climate sensor130 is designed to determine the temperature, air pressure, airhumidity, wind speed and/or amount of precipitation in the surroundingsof the first vehicle 1 and thus of the demarcating element 2. The milksensor 132 is designed to determine the amount and/or the composition ofmilk which is extracted from a dairy animal (not shown) in a milkingdevice (not shown).

In use, the 2D/3D camera 100 will form an image of the area which is tobe demarcated and/or has been demarcated, in this example a part of thepasture which has been grazed on and a part of the pasture which has notyet been grazed on, respectively. In addition, the 2D/3D camera 100 canform an image of the boundaries of these areas which, for example, maybe in the form of the fence 4 (FIG. 1), or the ditch 114 (FIG. 3). Inorder to produce a larger or differently oriented image, the controlsystem 120 can turn the 2D/3D camera 100 by one of the actuating motors.

Based on the image of the part of the pasture which has already beengrazed on, the control system 120 is able to determine to what extentthe amount of available grass has already been grazed off. To this end,use is advantageously made of the depth information of the 2D/3D camera100. On the basis thereof, the control system 120 decide whether thefirst 1 and/or second 10 vehicle should be moved, and also by how muchand in which direction they should be moved.

Based on the image of the 2D/3D camera 100 of the first vehicle 1, thecontrol system 120 determines the distance and orientation of the fence4 (FIG. 1), or the ditch 114 (FIG. 3) with respect to the first vehicle1. On the basis thereof, the motors 9 are driven in such a manner thatthe first vehicle 1 drives along the fence or ditch at a predetermineddistance therefrom. In this case, it is advantageous that the controlsystem 120 starts from the actual course of the fence or ditch. If, forexample, the course of the fence were to be modified, then, according tothe prior art, this could result in the first vehicle 1 not followingthe fence anymore or in fact colliding with the latter.

Furthermore, the system according to the invention is more flexible anduser-friendly than that according to the prior art. If a user moves afence, digs or fills a ditch, or modifies the area in any other way, hedoes not have to incorporate these changes in the predetermined patternfor remotely controlling the unmanned vehicles. Thanks to the 2D/3Dcamera 100, the system will automatically detect the relevant changes.

In addition, from the images from the 2D/3D camera 100, the controlsystem 120 can deduce whether cows are present and at what distance tothe first unmanned vehicle 1 these are located. Based on thisinformation, collisions with cows can be prevented. The control system120 can also deduce from the images how many cows there are. To thisend, it is advantageous to use several images over a period of time, orimages from several 2D/3D cameras 100. After all, cows may, viewed fromthe 2D/3D camera 100, be located behind other cows, as a result of whichnot all cows can be observed simultaneously by one 2D/3D camera 100.

Furthermore, the control system 120 is able to deduce from the imageshow the cows are distributed over the area. If a substantial number ofthe cows is distributed over substantially the entire area which hasbeen made available, this means that sufficient grass is available. If asubstantial number of the cows are near the demarcating element 2, thismeans that there is insufficient grass available in the area which hasbeen made available. This is an indication that an additional strip ofpasture has to be made available and thus that the unmanned vehicles 1,10 have to be moved.

The control system can also estimate from the images the remainingamount of grass in that part of the pasture which has been madeavailable to the cows and the amount of grass which is available in thepart which is still closed off. The control system 120 can then adjustthe amount of grass which is made available on the basis of the numberof cows which are present, the remaining amount of grass and/or theavailable amount of grass in the part which is still closed off.

Based on the information from the climate sensor 130, the control system120 can, if desired, produce an estimate of the speed at which the grassis expected to grow. This estimate may, in part, determine the point intime and/or the amount by which the demarcating element 2 is moved next.In addition, it is also possible to determine the amount of grass theanimals present in the demarcated area require on the basis of thesignals from the climate sensor 130. As an example, this need will beless great in extremely hot weather than with more moderatetemperatures.

The data from the milk sensor 132 can be used to determine the amountand/or composition of the milk produced by every individual dairy animalwhich is present in the demarcated area and/or for the total number ofthese dairy animals. If the amount of milk produced is small for a groupof this size and/or if the milk is of low quality, this forms anindication that too little grass was eaten and may be a factorindicating to the control system 120 to make a larger new area availablethan on the previous occasion using the vehicles 1 and 10 and thedemarcating element 2. It is also possible to bring the point in time atwhich a part of the area is made available forward.

While the first vehicle 1 is driving, the second vehicle 10 may remainstationary or drive at the same time. In both cases, the length of thewire 2 can be adjusted to a varying distance between the two vehicles 1,10 by means of the motor 12 of the tensioning device 11. It is alsopossible for one of the two, or for both 2D/3D cameras 100 to observethe wire 2 in order to determine whether the latter is sagging too muchor is, on the contrary, very taut. As a result thereof, in a variantwhich is not shown, the angle gauge 21 and/or the load cell canadvantageously be omitted. The driving of the second vehicle 10 ispreferably controlled based on images of its own 2D/3D camera 100, itbeing possible for the relevant control systems 120 to match thedisplacements of the first 1 and second 10 vehicles with one another bycommunicating with one another directly or via the PC 126.

Various variants are possible without departing from the scope of theinvention. Thus, it is possible to provide only the first vehicle withthe camera, the second vehicle for example being driven on the basis ofthe images from and/or the displacement of the first vehicle. It is alsopossible to use another demarcating element, such as non-electrifiedwire, barbed wire or mesh, instead of electrified wire.

The vehicle control unit or the control system is able to control thevehicles completely autonomously. It is also possible for part of theabove-described tasks of the vehicle control unit, such as determiningthe movement speed, duration and frequency of the vehicles, to becarried out by means of a computer which is operatively connected to thevehicle control unit. Instead of one central processing unit for eachunmanned vehicle, it is also possible to provide a single centralprocessing unit which controls several unmanned vehicles.

The central processing unit may comprise a programmable unit, but may,for example, also be composed of non-programmable logic circuits and/orof memories which can only be programmed to a limited extent, such as an(E)EPROM. The vehicle control unit or control system is designed tocarry out the above-described tasks. A customary method of producing acontrol unit is by programming it by means of software. Alternatively,or in combination with specific software, the control unit may also becompletely or partly composed of electronic components comprisingpreviously provided circuits for carrying out (part of) theabove-described tasks. In other words, the control unit can be equippedto carry out its tasks by means of software and/or specific hardware.

It is also possible to use a 2D camera, a pair of 2D cameras, or a 3Dcamera without 2D functionality instead of a combined 2D/3D camera.Instead of a 2D/3D camera on one or more vehicles, a 2D/3D camera canalso be provided separately. It is also possible to use a passiveinfrared camera, for example for observing dairy animals, instead of a2D/3D camera.

The 2D/3D camera can be provided on an observation vehicle which is notsimultaneously being used to attach a demarcating element on. Such anobservation vehicle may be an earth-bound vehicle, or an airbornevessel. The 2D/3D camera may also be provided at a fixed point in ornear the area to be demarcated.

Instead of using two vehicles, it is also possible to use one vehicleand a fixed point in the area, for example a post of the fence goingaround the pasture. When the one vehicle is driving, the distance to thefixed point may change, and the tensioning device will adjust the lengthof the demarcating elements accordingly. The fixed point may bedisplaced periodically by, for example, manually attaching the relevantend of the demarcating elements to another post.

The motor driving the unmanned vehicle can be an electric motor or acombustion engine. The motor does not have to be inside the vehicle, butmay also be, for example, at a fixed point in or near the area and beconnected to the vehicle via a drive element, such as a cable.

Instead of being directly connected to the central processing unit, theobservation devices can also be connected to the PC. Also, the controlsystem may be connected to other observation devices than the onesshown, it even being possible for these observation devices themselvesto be at a distance to the respective area to be demarcated. Suchobservation devices may be situated, for example, on board an airplaneor satellite, or may be climate sensors at a climatological institute.Such a climatological institute could also preprocess climate data toproduce, for example, a signal which is representative of the expectedgrowth rate of the grass.

It is also possible for at least one dairy animal, some of the dairyanimals or all of the dairy animals to be provided with a GPS receiverand a transmitter for transmitting the current situation of the dairyanimals in question. Furthermore, the system may be provided with a feeddispensing sensor for observing the dispensing of solid and/or liquidfeed to an animal, also including water. Thus, the control system isable to adapt the amount of grass to be made available to the amount ofother feed which has been dispensed.

The dairy animals may also be provided with a feeding sensor which, incombination with the position information, also makes it possible todetermine whether or not the dairy animal in question is feeding or not.The information of the GPS receiver and/or of the feeding sensor may,together with or instead of, the information from the 2D/3D camera beprocessed in the control system in order to determine whether and wherethe cows are feeding, which information can be used in order todetermine whether, when, and by what distance the demarcating elementhas to be moved by one or more vehicles.

Thus, the invention has been described by reference to certainembodiments discussed above. It will be recognized that theseembodiments are susceptible to various modifications and alternativeforms well known to those of skill in the art. Accordingly, althoughspecific embodiments have been described, these are examples only andare not limiting upon the scope of the invention. The person skilled inthe art will be able to apply various modifications and adaptationswithin the scope of the invention, the scope of protection for theinvention being determined by the accompanying claims.

1. A system for demarcating an area, the system comprising: a movabledemarcating element; a control system for determining at least one ofthe magnitude and the moment of a next move of the movable demarcatingelement; and one or more observation devices for observing an entitynear the movable demarcating element, wherein the one or moreobservation devices are operatively connected to the control system fortransmitting a signal from the one or more observation devices to thecontrol system, and wherein the control system is for receiving andprocessing the signal from the one or more observation devices todetermine at least one of the magnitude and the moment of the next moveof the movable demarcating element.
 2. The system as claimed in claim 1,wherein the one or more observation devices comprise at least one of thefollowing: a light sensor, a climate sensor, a milk sensor, a soundsensor, a feed-dispensing sensor, and a position sensor connected to ananimal.
 3. The system as claimed in claim 2, wherein the milk sensor isfor measuring an amount of milk produced by at least one dairy animal.4. The system as claimed in claim 2, wherein the milk sensor is formeasuring the composition of the milk produced by at least one dairyanimal.
 5. The system as claimed in claim 1, wherein the one or moreobservation devices comprise a camera for forming an image of thesurroundings of the movable demarcating element.
 6. The system asclaimed in claim 5, wherein the camera comprises: a source of radiationfor emitting electromagnetic radiation; a matrix having several rows andseveral columns of receivers for receiving electromagnetic radiationreflected by an object; a lens for displaying the reflectedelectromagnetic radiation on the receivers; and a sensor control unitoperatively connected to the source of radiation for modulating theelectromagnetic radiation, for determining a phase difference for eachof the receivers between the emitted and the reflected electromagneticradiation.
 7. The system as claimed in claim 1, further comprising afirst vehicle and wherein the control system is for transmitting acontrol signal to the first vehicle for moving the demarcating element.8. The system as claimed in claim 1, wherein the one or more observationdevices are for observing a position of a dairy animal or an amount ofgrass in the area.
 9. A method for demarcating an area, the methodcomprising: providing a movable demarcating element, a control system,and one or more observation devices operatively connected to the controlsystem; observing via the one or more observation devices, an entitynear the movable demarcating element; transmitting a signal from the oneor more observation devices to the control system; receiving in thecontrol system the signal from the one or more observation devices; andprocessing the signal to determine at least one of the magnitude and themoment of the next move of the movable demarcating element.
 10. Themethod as claimed in claim 9, wherein the step of observing via the oneor more observation devices comprises observing using at least one ofthe following: a light sensor, a climate sensor, a milk sensor, a soundsensor, a feed-dispensing sensor, and a position sensor connected to ananimal.
 11. The method as claimed in claim 10, wherein the step ofobserving via the one or more observation devices comprises measuring anamount of milk produced by at least one dairy animal.
 12. The method asclaimed in claim 10, wherein the step of observing via the one or moreobservation devices comprises measuring the composition of the milkproduced by at least one dairy animal.
 13. The method as claimed inclaim 9, wherein the step of observing via the one or more observationdevices comprises forming an image of the surroundings of the movabledemarcating element.
 14. The method as claimed in claim 9, wherein thecamera comprises a source of radiation for emitting electromagneticradiation, a matrix having a plurality of rows and columns of receivers,a lens, and a sensor control unit operatively connected to the source ofradiation, and wherein the method further comprises: emittingelectromagnetic radiation from the source of radiation; receivingelectromagnetic radiation reflected by an object using the receivers;displaying the reflected electromagnetic radiation using the lens;modulating the electromagnetic radiation using the sensor control unit;and determining a phase difference between the emitted and the reflectedelectromagnetic radiation for each of the receivers.
 15. The method asclaimed in claim 9, further comprising providing a first vehicle andtransmitting a control signal to the first vehicle for moving thedemarcating element.
 16. The method as claimed in claim 9, wherein thestep of observing via the one or more observation devices comprisesobserving a position of a dairy animal or an amount of grass in thearea.